Container with twist-off closure

ABSTRACT

A container comprises a releasable metal closure  14  formed with an end wall  15  and a depending skirt  16  and having an annular layer  18  of sealing compound provided on the inside of the end wall adjacent the skirt and a container body  1  comprising a neck  2  with an annular sealing surface  4  surrounding a circular opening and adapted to seal against the annular layer of sealing compound over an annular sealing interface in the closed position of the closure on the container body. The container body  1  and the closure  14  are formed with no mechanical means for coupling them together to form or maintain a seal therebetween and the seal is provided by a partial vacuum formed in the container during processing. The annular sealing surface  4  of the container body  1  is formed with a localised protrusion  5  or recess  10  which provides a discontinuity in the annular sealing interface, whereby relative rotation of the closure  14  and container body  1  from the closed position creates a venting path from the interior of the container body to the exterior so that the seal is broken and the closure is released.

TECHNICAL FIELD

The invention relates to a container comprising a glass container bodyand a releasable metal closure containing an annular layer of sealingcompound.

BACKGROUND ART

Containers are well known in which a metal, releasable cap closureTraditionally, the cap is screw fitted onto the body such that the uppersurface of the neck of the container seals against the layer of sealingcompound. Filling speeds for such containers are generally up to about500 containers per minute.

Because of the time taken to fit a screw closure during production, amodified arrangement has been developed in which a closure is formedwith sealing compound moulded to the outer part of the closure end walland to the inside of the closure sidewall or skirt. This kind of closuremay be push fitted onto a screw threaded container during production ofa filled container. Filling speeds for such containers may be up toabout 1,000 containers per minute. The screw threads of the body diginto the sealing compound to form at least a partial thread therein suchthat, when the container comes to be opened, relative rotation of theclosure and container body will break the seal and allow the closure tobe removed. This arrangement is useful for certain food products where apartial vacuum is maintained in the container after filling and closure.During the filling process of the container, steam is injected into theopen container in the head space above the hot food product which hasbeen measured into the container. The closure is then pressed down ontothe container and, as the steam condenses, a partial vacuum is formed inthe container above the head space which acts to hold the closure firmlyin place on the container body. In the fully cooled filled container,the typical vacuum in the container is about 0.3 bar. This partialvacuum must be vented to allow the cap closure to be removed.

In another known container, a glass container body in the form of aglass tumbler is formed with an annular bead around its upper end. Thetumbler body is molded and then treated to melt its upper end edge toform the bead which is smooth for drinking. A flexible aluminium closureis snapped over the bead and forms a seal with the body by virtue of apartial vacuum formed in container during processing. The seal is brokenby prying off the closure.

A steel closure cannot be used in this arrangement since steel is notsufficiently flexible for use in a pry-off closure.

DISCLOSURE OF INVENTION

The invention provides a container which can be opened by twisting theclosure in which neither the container, nor the closure needs to beprovided with a screw thread nor any other mechanical engagement meansfor securing the closure to the body. In the arrangement of the presentinvention, the closure is held on the container body by virtue of thepartial vacuum formed in the container body during processing of thecontainer to fill it with a food or beverage product. The container bodyis provided with a discontinuity on its annular sealing surface whichcauses the interior of the body to be vented when the closure is rotatedfrom the original closed position so that the seal is broken and theclosure is released.

According to the invention, there is provided a container comprising: areleasable metal closure formed with an end wall and a depending skirtand having an annular layer of sealing compound provided on the insideof the end wall adjacent the skirt; and a glass container bodycomprising a neck with an annular sealing surface surrounding a circularopening and adapted to seal against the annular layer of sealingcompound over an annular sealing interface in the closed position of theclosure on the container body; wherein the container body and theclosure are formed with no mechanical means for coupling them togetherto form or maintain a seal therebetween and the seal is provided by apartial vacuum formed in the container during processing; wherein theannular sealing surface of the container body is formed with a localisedprotrusion or recess which provides a discontinuity in the annularsealing interface; whereby relative rotation of the closure andcontainer body from the closed position creates a venting path from theinterior of the container body to the exterior so that the seal isbroken and the closure is released.

The invention provides several advantages.

It is not necessary to provide a screw thread on the container neck.This greatly simplifies manufacture of the container body and saves onmaterial since a shorter neck can be provided.

Having only an annular layer of sealing compound on the end wall of thecap closure means that the sealing compound need not be moulded but canform under gravity. This uses less compound, greatly simplifiesmanufacture and removes the scrap generated in the compound mouldingprocess.

Since the cap closure does not require lugs to engage a thread, a verysmall radial gap can be provided between the skirt of the closure andthe neck of the container body. This reduces the risk of ingress offoreign matter, bugs, etc. and also increases resistance to accidentaldamage.

The absence of any threads on the cap means it can have reduced height,thus saving in material.

Since the closure is removed by twisting rather than being pried off, itcan be made of steel. Steel closures are sufficiently elastic to beformed with vacuum indicating buttons. Thus containers in accordancewith the invention can be used with a wide variety of food and beverageproducts.

The torque required to open a container made in accordance with theinvention is considerably less than typically required to open athreaded container. For example, the opening torque for a 51 mm closurehas been reduced from about 3.4 Nm to only about 1.0 Nm. Reduction inthe opening torque allows the use of fewer lubricants in the compound.These lubricants are one of the principle causes of migration into thefood during processing. Thus, the new design also has benefits for foodsafety.

BRIEF DESCRIPTION OF DRAWINGS

Embodiments of the invention are described below with reference to theaccompanying drawings, in which:

FIG. 1 is an isometric view of the top portion of a first containerbody;

FIG. 2 is an enlarged view of part of the neck of the body;

FIG. 3 is a partial section showing the profile of a protrusion formedon the annular sealing surface of the body;

FIG. 4 is a isometric view of the top portion of a second containerbody;

FIG. 5 is an enlarged view of part of the neck of the second body;

FIG. 6 is a partial section showing the profile of a recess formed onthe annular sealing surface of the second body;

FIG. 7 is an isometric view, partially cut away, of the top portion ofthe first container body provided with a closure;

FIG. 8 is an isometric view, partially cut away, of the top portion ofthe second container body provided with a closure;

FIG. 9 is a radial sectional view through the neck of the firstcontainer and the closure;

FIG. 10 is a circumferential sectional view through part of the firstcontainer and closure in the closed portion;

FIG. 11 is a circumferential sectional view through part of the firstcontainer and closure after relative rotation;

FIG. 12 is an isometric view of variant of the second container body;

FIG. 13 is a radial section view through the top portion of thecontainer and a closure taken at the point A of FIG. 12; and

FIG. 14 is a view similar to FIG. 13 taken at the point B of FIG. 12.

MODE(S) FRO CARRYING OUT THE INVENTION

A first embodiment, shown in FIGS. 1 to 3, 7 and 9, comprises a glasscontainer body 1 having a neck 2 with a circular opening 3 surrounded byan upper rim which defines an annular sealing surface 4 which isprovided primarily by the generally flat top edge face 4 a of the neckand also by the upper parts of the inner and outer surfaces 4 b, 4 c ofthe neck. A venting feature comprising a localised discontinuity in thesurface 4 is provided by a small protrusion 5 which extends generallyradially across the surface 4 so as to extend downwardly beyond thereach of the annular layer of sealing compound when a closure is fittedas best seen in FIG. 9 so that it extends continuously from the interiorof the container body to the exterior of the container body. Theprotrusion has a curved circumferential profile generally comprising anupslope 7, a curved top 8 and a downslope 9. The upslope 7 is inclinedto the surface 4 at an angle θ which is less than 30°. The angle θ is onthe trailing edge so that a jar can be opened by rotating the closureconventionally anti-clockwise.

In one embodiment the container neck has an external diameter of about51 mm and the protrusion has a circumferential length of about 1.0 mmand a height of about 0.2 mm. All the radiuses on the protrusion areabout 0.2 mm. This is so the features can press into the soft sealingcompound to create a continuous sealing surface during capping. Such acontainer body may be moulded from glass.

In a second embodiment, shown in FIGS. 4 to 6 and 8, the discontinuityis provided by a shallow recess or groove 10 having a continuouslycurved surface 11. The recess again extends radially across the sealingsurface 4 and partially down the inner and outer surfaces 4 b, 4 c ofthe neck 2 so that it extends continuously from the interior of thecontainer body to the exterior of the container body.

The shallow recess 10 has a circumferential length of about 5 mm and adepth of about 0.2 mm. In a preferred embodiment the profile of therecess is part circular with a radius of about 16 mm. Thus, the recessin the annular sealing surface 4 is part cylindrical.

A variant of the second embodiment is shown in FIGS. 12 to 14. In thisembodiment, the container body is in the form of a glass tumbler havingan annular bead 20 around its upper end. One or more shallow recesses 10are formed in the radial outer face of the bead. The recess in thisvariant has a depth of about 0.4 mm.

The closure may be formed with a plurality of lobes at the bottom of theskirt. These lobes form clips which provide a loose snap-over fit withthe bead of the body to assist in re-fitting the closure after opening.They do not, however, play any part in making a seal between the closureand the container body and must be pushed upwardly past the bead afterthe seal has been broken.

Releasable closures 14 (of type known as vacuum closures) for the firstand second containers are shown in FIGS. 7 and 8 and comprise an endwall 15 and a depending skirt 16. The end wall has a central pop-uppanel known as a “vacuum button” 17 which is normally held in a concaveshape by the partial vacuum in the closed container. The button pops-upto a convex shape to give a warning that the vacuum has been vented andthus the seal has been broken. An annular layer 18 of sealing compoundis formed on the inside of the closure end wall adjacent the skirt 16.This layer of compound seals against the annular sealing surface 4 ofthe container neck over an annular sealing interface in the closedposition of the closure 14 on the body 1. The sealing compound is PVCplastisol and is applied to the closure through a nozzle and allowed tosettle under gravity to form a generally even annular layer. It is curedbefore the filling process but will be softened during the filling andcapping process by the steam in the head space above the food product sothat it can flow around or into the venting feature 5, 10 and set aroundthe annular sealing surface 4.

Other flowed materials are available to avoid the use of PVC, andcompound gaskets may also be made from injection moulded or compressionmoulded thermoplastics or thermoplastic elastomers. In some cases aseparate disc or ring of elastomeric material is inserted into theclosure to form the compound gasket.

During capping the compound is typically heated and applied with anaxial load so that it deforms to the jar profile to create a gas tightseal. The jar may then be processed by pasteurisation or sterilisationto provided extended shelf life of the product. During capping,processing or subsequent storage and distribution the compound typicallytakes a permanent set so that the profile when opened is different tothe original uncapped profile.

To aid opening the compound often includes a lubricant material toreduce the coefficient of friction between the glass gar and compound.

An enlarged sectional view through part of the first container andclosure in the closed position is shown in FIG. 10. As can be seen, theprotrusion 5 extends upwardly across the annular sealing interface andpartially into the layer 18 of sealing compound. During capping of thefilled container, the sealing compound deforms so that its thicknessbetween the closure end wall 15 and the upper edge of the containerreduces. Typically, this reduction is from about 1 mm to about 0.5 mm.The height of the protrusion 5 is less than the thickness of the layerof sealing compound after fitting of the closure to the container body.When the closure 14 is rotated relative to the container body (it willbe natural for the closure to be rotated anti-clockwise since consumersare accustomed to opening containers in this way) venting of the vacuumin the container takes place. Venting takes place because there is apath created between the compound and container. After venting andfurther rotation the closure moves away from the container as shown inFIG. 11.

Prior to capping, a food or beverage product is put into the containerand steam is injected into the headspace above the product. The closurecap is then pressed downwardly onto the container body so that a seal isformed. The inserted steam rapidly condenses and this forms a partialvacuum in the headspace to hold the closure firmly on the containerbody.

Following capping, the filled container is then normally processedaccording to the required food preservation conditions, for exampleproducts high in sugar, acid or salt may just need to be hot filled orpasteurised at 85 to 100° C. whereas meat based products which have nonatural preservatives require a full sterilisation process at 121 to130° C. to preserve the food product. Specific compound types have beendeveloped to meet the differing processing conditions, for example ablown compound is typically used for pasteurised products as this hasentrapped pockets of gas within the sealing layer which make thecompound flexible in order to conform to the sealing surface atrelatively low temperatures. For sterilised products less or no blowingagents may be used in order to form a stiffer sealing layer which ismore resilient and suitable for higher temperature processing. Theinventors have found that the stiffer non blown materials areparticularly suitable for creating a venting feature. In this case thecompound better retains the shape memory of the discontinuity afterprocessing and forms a stable vent path when the cap is first rotated.

Opening of the second container takes place in a similar manner. In thisembodiment, the sealing compound extends downwardly across the annularsealing interface and fills the recess 10. The depth of the recess mustbe less than the difference in the depth of the layer of sealingcompound before and after fitting of the closure. This ensures that therecess is completely filled with sealing compound.

When the closure is rotated, a path is created between the sealingcompound and the container since the two surfaces no longer conform toeach other.

The container bodies 1 of the first and second containers are made ofglass and the closures are made of metal, preferably steel.

It is preferred that only a single venting feature is provided for tworeasons; firstly, there is a load induced by each feature so having justone reduces the overall load. Secondly, the axial load required forlifting the panel against the vacuum is lower if it is only on one side.Two or more may be provided but it is believed that the best solution isto have only one since this reduces the torque required to open thecontainer.

It will be understood that the closure cannot be properly resealed tothe container body after opening and release of the vacuum. Thisarrangement is appropriate for food products which should be consumedimmediately once the container has been opened although the closure maybe replaced on the container and used as a cover, for example where foodis stored in the fridge.

The body 1 and closure 14 are formed with no mechanical engagement meansfor coupling them together to form or maintain a seal therebetween andthe seal is provided by a partial vacuum formed in the container duringprocessing. In particular, the closure is not threaded or crimped ontothe container body.

1. A container comprising; a releasable metal closure formed with an endwall and a depending skirt and having an annular layer of sealingcompound provided on the inside of the end wall adjacent the skirt; anda glass container body comprising a neck with an annular sealing surfacesurrounding a circular opening and adapted to seal against the annularlayer of sealing compound over an annular sealing interface in theclosed position of the closure on the container body; wherein thecontainer body and the closure are formed with no mechanical means forcoupling them together to form or maintain a seal therebetween and theseal is provided by a partial vacuum formed in the container duringprocessing; wherein the annular sealing surface of the container body isformed with a localised protrusion or recess which provides adiscontinuity in the annular sealing interface; whereby relativerotation of the closure and the container body from the closed positioncreates a venting path from the interior of the container body to theexterior so that the seal is broken and the closure is released.
 2. Acontainer as claimed in claim 1, wherein the discontinuity provided bythe protrusion or recess on the annular sealing surface extendscontinuously from the interior of the container body to the exterior ofthe container body.
 3. A container as claimed in claim 1, wherein thediscontinuity is provided by a protrusion on the annular sealing surfacewhich extends into the layer of sealing compound in the closed positionof the closure on the container body.
 4. A container as claimed in claim3, wherein the protrusion extends generally radially across the annularsealing surface.
 5. A container as claimed in claim 4, wherein theprotrusion has a curved profile generally comprising an upslope, acurved top and a downslope, wherein the upslope is inclined to theannular sealing surface at an angle θ of less than 30°.
 6. A containeras claimed in claim 1, wherein the discontinuity is provided by a recessin the form of a groove in the annular sealing surface and the sealingcompound of the closure extends into and at least partially fills thegroove.
 7. A container as claimed in claim 1, wherein the protrusion orgroove is generally smooth such that radii on the protrusion or recessare at least as large as the depth or height of the feature.
 8. Thecontainer as claimed in claim 1, wherein the sealing material is formedfor a solid (non blown) material which takes a permanent set duringprocessing such that, when cooled and the container is opened, aphysical vent path is retained in the sealing material.
 9. The containeras claimed in claim 1, wherein the height of the protrusion is less thanthe thickness of the layer of sealing compound after the closure hasbeen fitted to the container.
 10. The container as claimed in claim 1,wherein the depth of the groove is less than the difference in thethickness of the sealing layer before and after fitting of the closure.11. The container as claimed in claim 1, wherein only one discontinuityis present on the sealing surface so as to create an eccentric forcewhich breaks the vacuum on opening.
 12. The container as claimed inclaim 1, further comprising multiple discontinuities which form severalvent features and thereby increase the rate of venting.